Sterilising machines and the like



Dec. 31, 1957 I A. }H. WEBSTER STERILISING MACHINES AND THE LIKE Filed Oct. 18, 1955 2 Sheets-Sheet 1 Inventor By 7 47 7 Attorneys 31; 1957 A. H. WEBSTER 2,818,012

STERILISING MACHINES AND THE LIKE Filed Oct. 18, 1955 2 Sheets-Sheet 2v Inventor r? H WElssrz/e A ttorneys United States Patent STERILISING MACHINES AND THE LIKE Alexander Hyde Webster, London, England, assignor to R. W. Webster and Company Limited, Waltham Cross, England, a British company Application October 18, 1955, Serial No. 541,246

Claims priority, application Great Britain November 4, 1954 7 Claims. (Cl. 99362) This invention relates to sterilising machines and the like such as used for processing encased foodstufls, bottled milk or liquids, and the like.

A well-known type of sterilising machine to which the present invention is directed comprises a closed chamber into and from which cans, bottles or the like under treatment are carried through one or more U-shaped passages communicating with the chamber and filled with liquid to seal off the chamber from the atmosphere. The chamher is maintained at a high temperature, e. g., by steam injected into it and/or generated therein, and this steam may be maintained under pressure by a difference in the levels of the liquid in the inner and outer limbs of the, or each, U-shaped sealing conduit. The bottles, cans or like articles being treated are mounted on an endless conveyor belt or chain and carried thereby through the inlet sealing conduit, to and through the sterlising chamber, and out through the outlet sealing conduit. It will be appreciated that the liquid at the top of the inner limb of each U-shaped sealing conduit is at a comparatively high temperature (comparable with that of the sterilising chamber) while the liquid at the top of the outer limb of each U-shaped sealing conduit is at a much lower temperature, and that a temperature gradient through the sealing conduit exists between these two extremes. The articles under treatment thus enter the liquid seal at a comparatively low temperature, and are gradually heated, during passage through the seal into the sterilising chambers, and gradually cooled during like passage out of the machine. Typical conditions for a machine intended, for example, to sterilise liquid milk in bottles consist in an internal temperature in the sterilising chamber of 230 F. wet steam requiring a pressure above atmosphere of about 6 lbs. per square inch, maintained by a head of about 14 ft. of water in the U-shaped sealing conduits. The desirable and permissible temperature of the water at the outer water surface of the inlet sealing conduit may be of the order of 180 F.

It will be appreciated that in a U-shaped sealing conduit such as described above convection currents will tend to arise in the outer limb of the conduit liable to disturb the temperature gradient and working conditions, since the warmer and less dense water at the base of the column will tend to rise while the cooler and denser water at the top will tend to fall, resulting in intermixing and more uniform heat distribution. In the inner limb of the sealing conduit on the other hand the water is heated by steam pipes or injected steam and tends to rise to the top of this column, opening into the sterilising chamber, which is desirable. The heating means are purposely located in such a position in the inner column of the sealing conduit as to avoid passage of heat and/or hot water to the outer sealing column where its presence might cause rupture of the seal due to its conversion to steam upon reaching a zone of pressure below the equilibrium pressure corresponding to its temperature.

In knownmachines therefore there is a tendency for the outer column of a seal to become of comparatively uniform temperature, and the inner column of the seal to be maintained at a comparatively high temperature, with the result that at the bottom of the seal the articles carried by the conveyor may encounter a comparatively abrupt and undesirably large change of temperature, and not to be subject to adequate heat exchange during comparatively long passage through the outer column of the seal.

One object of the present invention is to provide a sterilising machine free from the aforesaid defect, and with this end in view the invention consists in a sterilising machine of the kind comprising a heated sterilising chamber closed to the atmosphere by a U-shaped liquid seal communicating with the chamber, and adapted to maintain a pressure within the chamber by a difference of liquid level in the two limbs of the seal, wherein the outer column of the U-shaped seal is stepped or formed of a plurality of misaligned portions whereby to eliminate a direct vertical path through the full length of this column. In this way the ascent of heated liquid from the bottom to the top of this column is prevented or reduced, and the column is constituted by zones at different, progressively varying, temperatures more suitable for treatment of the bottles or like articles passing therethrough. This arrangement also allows the provision and selection of injection points for heat and/or of thermostatic control means, adapted to set up and maintain desired working conditions. The arrangement may be incorporated in either or both the inlet seal and the outlet seal of a sterilising machine.

In many known sterilising machines it is common practice for the conveyor chain to hold the bottles, jars or the like located in pockets therein, and for the chain to move linearly and usually vertically as it is passed through the machine. The bottles, jars or the like do not therefore vary in attitude while passing through the machine except at the turning points of the conveyor chain i. e. at cornparatively infrequent interval-s. It is known that more uniform heating of the contents is achieved if the contents are gently disturbed during sterilisation and another object of the present invention is to achieve that result.

With this end in view the invention consists in a sterilising machine comprising a conveyor adapted to receive bottles, cans or the like and convey them along the serpentine or zig-zag path through a sterilising chamber, wherein the conveyor is adapted over at least part of its travel between successive turning points of the said serpentine or zig-Zag path to follow a non-linear path whereby the bottles, jars or the like are repeatedly tilted and the contents disturbed during passage through the machine. The conveyor may, for example, be arranged, during a generally vertical movement in the machine, to follow a wavy or sinuous path in relation to the vertical so that as it conforms with the various changes of direction the bottles or the like carried by it are longitudinally tilted to various angles above and below the horizontal.

The invention will be clearly understood from the following description of forms (given, however, merely by way of example) which it may assume, and this description will be more readily followed by reference to the drawings herewith:

Figures 1-3 represent in side sectional elevation, and somewhat diagrammatically, three forms of steriliser incorporating the invention.

in carrying the invention into eifect in one convenient manner, as shown in Figure l of the aforesaid drawings. a sterilising machine comprises a sterilising chamber 1 with which communicates a U-shaped inlet conduit having an outer leg 2 and inner leg 3, and a like U-shaped outlet conduit having an outer leg 4 and inner leg 5. A conveyor chain 6 is provided in known manner with pockets adapted each to receive a. bottle and to hold it in an attitude such that the axis of the bottle is substantially perpendicular to the chain. The chain traverses the path indicated by arrows to carry the bottles through the inlet seal, the sterilising chamber and the outlet seal, and it may also in its return path carry the bottles through the usual cooling tank 7 beneath the sterilising chamber.

The chain in known machines normally follows linear vertical paths, and it will be seen that in this case, except at the turns of the chain from one upward vertical path to the next downward vertical path, or vice versa, the bottles in the chain remain untilted and substantially horizontal.

According to one feature of the present invention the guides, rollers or the like whereby the path of the chain is determined are so arranged that the chain follows a. non linear path in its ascent and descent within the machine. For example in the inlet seal the path of the chain may be outwardly curved as at 8, and at a lower level inwardly curved as at 9. Similar curvature of the path of the chain may be provided in the runs within the chamber and in the outlet seal as shown. If necessary the walls and/or partitions may be curved, as at 10, to accommodate curvature of the chain. The runs of chain are not restricted to a single curved section as shown but may, if desired, be formed with several curved portions in each run, or may follow a generally wavy or sinuous path. It will be seen that with this arrangement each bottle in passing through the machine is rocked or tilted in relation to the horizontal, and this has the effect of improving the transfer of heat to, and distribution of heat in, the contents of the bottle, and of ensuring uniform processing of the contents.

In a machine such as illustrated in Figure 1 (whether or not the conveyor chain follows a. curved path as there shown), it is usual to heat the water in the inlet seal by injecting heat at the point marked B and the pressure head of liquid in the sealing column may be such that the temperature inside the sterilising chamber (and thus at the top surface C of the inner leg of the sealing column) is about 230 C. The temperature of the water at the top surface A of the outer leg of the seal may be about 180 F.-l90 F.

It has been observed that the temperature of the water at a point such as D at the foot of the outer leg of the seal is often not appreciably greater than the temperature at point A, and it follows therefore that bottles entering the seal when at a temperature of, say, l50-l60 F. receive comparatively little heat during their passage from A to D, but are thereafter subjected to substantial temperature changes from D to C. These conditions give rise to the danger of bottle breakage between points D and C; and also indicate that the bottle may be inefficiently treated because it or its contents may not have reached a temperature of 230 F. upon arrival at point C owing to the inefiiciency of heating in the outer leg of the inlet seal, and the comparatively short time of passage through the inner leg.

According to another feature of the invention means are provided to reduce or eliminate the aforesaid defect in known machines. One form of the invention embodying this feature is shown in Figure 2 of the abovementioned drawings wherein the same references as in Figure 1 indicate the same features.

As will be seen from Figure 2 the inlet seal, and preferably also the outlet seal, of a sterilising chamber comprise a plurality of sections or portions which are stepped or misaligned in a vertical direction. Thus the inlet seal comprises a lower vertical portion 11 communicating with an offset upper vertical portion 12, the side wall of which extends downwards to form a pocket E at the top of the lower portion 11.

As in known devices heat is injected at B to maintain the desired internal temperatures; and in accordance with this feature of the invention further heat injection may be effected at the foot of the outer limb of the seal, e. g. at point D. Water heated at D may tend to rise but will mainly be trapped in the pocket E where, being under pressure from the water in the upper portion 12 of the sealing column it can be maintained at a quite high temperature, say 212 F.

Thus by the arrangement described it is possible to set up an intermediate zone of water at a temperature of, say, 210-220 F. which will be stable and will be retained by the offset or stepped portions of the conduit from convective movement to mix, and exchange heat, with the cooler water in the upper zone between points l5 and A.

Similar considerationsapply tothe outlet sealing column which may be similarly formed, as illustrated.

While as illustrated each sealing column is shown with a single step it is within the scope of the invention to provide two or more stepped portions in order to set up as many heating zones with progressively different temperatures as desired.

In our British patent specification No. 648,345 there is described an arrangement for stabilising a sealing column wherein cooler water is fed in as a blanket to the top of the sealing column and withdrawn from a slightly lower level in the column. This arrangement may be included in a sterilising machine incorporating either or both features of the present invention referred to above. It will be seen, however, that some of the cool water injected at the top of the upper section 12 of the inlet sealing column may tend to descend, entering. the lower section 11 and disturbing the heat distribution desired. For the purpose of countering this danger the lower end of the upper section 12 may be extended downwards, beside the lower section 11, as indicated in dotted lines, whereby cool water descending from the top of the sealing column will pass into the extending lower portion of upper section 12 instead of into the lower section 11 where it is desired to maintain a higher temperature.

In Figure 3 of the abovementioned drawings is illustrated a sterilising machine incorporating both features of the invention discussed above, viz. a curved or sinuous path for the conveyor chain to ensure repeated tilting of the bottles during passages, and sealing columns formed of stepped or relatively misaligned vertical sections where by to facilitate maintenance of different heat zones at different levels in the seal. The manner of operation of the device shown in Figure 3 will be clearly understood by comparison with Figures 1 and 2.

In any of the machines described above may be incorporated the meansv for. controlling and interrelating the temperatures of the liquid at different points of the machine as described in British Patent No. 730,781.

Such arrangements facilitate a regenerative exchange of heat between the inlet and outlet seals which is frequently desired.

From the above description it will be seen that the aim of the invention is to ensure uniform distribution of heat in a sterilising machine in order to allow uniform heating and cooling of bottles and other containers passed therethrough, and thus to ensure efficient processing of the contents without any deleterious effects either to the contents or the containers. This end is achieved by employing either or both of two features, viz:

(a) A non-linear path for the conveyor chain which ensures separated rocking of the bottles or containers thereon and thus repeated disturbance of the contents; and

(b) A sealing. column (or each sealing column) formed of stepped or misaligned sections allowing zones of heated liquid at different temperatures to be maintained more readily than heretofore.

It follows from achievement of these results that bottles or containers can be treated at a greater speed than heretofore because there is reduced danger of breakage of bottles and/or spoiling of the contents, by too rapid temperature changes or too localised application of heat.

It should be understood that the invention is not restricted solely to the details of the forms described above, which may be modified in order to meet various conditions and requirements encountered, without departing from the scope of the invention.

What I claim is:

1. A sterilising machine comprising a closed heated sterilising chamber, a U-shaped passage communicating with the lower part of said chamber, liquid, forming a seal in said U-shaped passage, maintained at a higher level in the outer column than in the inner column of said U- shaped passage in order to maintain a superatmospheric pressure within said chamber, the outer column of said U-shaped passage being formed with a plurality of intercommunicating sections the axes of the said sections being parallel to one another, and each section being displaced sideways in relation to a neighbouring section in order to eliminate a rectilinear path through the full length of said column.

2. A sterilising machine comprising a closed heated sterilising chamber, a U-shaped passage communicating with the lower part of said chamber, liquid, forming a seal in said U-shaped passage, maintained at a higher level in the outer column than in the inner column of said U-shaped passage in order to maintain a superatmospheric pressure within said chamber, the outer column of said U-shaped passage being formed with a plurality of sections intercommunicating with one another, the axes of all said sections being vertical, the said sections being located at difierent levels above the base of the machine, and each section being displaced laterally in relation to an adjacent section.

3. A sterilising machine comprising a closed heated sterilising chamber, a U-shaped passage communicating with the lower part of said chamber, liquid forming a seal in said U-shaped passage maintained at a higher level in the outer column than in the inner column of said U- shaped passage in order to maintain a superatmospheric pressure within said chamber, the outer column of said U-shaped passage being formed with a plurality of substantially vertical sections intercommunicating with one another, located at different levels above the base of the machine, each section being displaced laterally in relation to an adjacent section, and a lower section of the U- shaped passage extending above the point at which it communicates with the adjacent upper section, and being closed at its upper end to form a trap for rising heated liquid.

4. A sterilising machine comprising a closed heated sterilising chamber, a U-shaped passage communicating with the lower part of said chamber, liquid forming a seal in said U-shaped passage maintained at a higher level in the outer column than in the inner column of said U- shaped passage in order to maintain a superatmospheric pressure within said chamber, the outer column of said U-shaped passage being formed with a plurality of substantially vertical sections intercommunicating with one another, located at dilferent levels above the base of the machine, each section being displaced laterally in relation to an adjacent section, and an upper section of the U-shaped passage extending below the point at which it communicates with the adjacent lower section, and being closed at its lower end to form a trap for cool liquid tending to sink.

5. A sterilising machine comprising a closed sterilising chamber, an endless conveyor, roller means in said sterilising chamber over which said conveyor is moved, so arranged that the conveyor follows a zig-zag path in successive substantially vertical directions upwards and downwards through said sterilising chamber, pockets in said conveyor for receiving substantially cylindrical containers with the axes of said containers substantially horizontal and substantially perpendicular to the transverse dimension of said conveyor, and means between at least two of the turning points of said zig-zag path whereby the conveyor is constrained to follow a non-linear wavy path whereby each cylindrical container carried by the conveyor is repeatedly rocked about a horizontal axis perpendicular to its own horizontal longitudinal axis, and the contents thus repeatedly disturbed in passing through the sterilising chamber.

6. A sterilising machine comprising a closed sterilising chamber, a U shaped liquid seal conduit communicating with the base of said chamber and having an outer limb extending in a generally vertical direction, an endless conveyor traversing said liquid seal conduit, pockets in said conveyor for receiving substantially cylindrical containers with the axes of said containers substantially horizontal and substantially perpendicular to the transverse dimension of said conveyor, and means between the upper and lower ends of said liquid-seal conduit whereby the conveyor is constrained to follow a non-linear wavy path whereby each cylindrical container carried by said conveyor is repeatedly rocked about a horizontal axis perpendicular to its own horizontal longitudinal axis, and the contents thus repeatedly disturbed during passage through said liquid seal conduit.

7. A sterilising machine according to claim 6 wherein said U-shaped liquid-seal conduit is formed with a curved wall to accommodate the sinuous passage therethrough of the conveyor.

References Cited in the file of this patent UNITED STATES PATENTS 994,192 Pinkney June 6, 1911 1,584,397 Paxton May 11, 1926 1,772,532 Ablertoli Aug. 12, 1930 1,952,419 Chapman Mar. 27, 1934 2,719,478 Vander Winden Oct. 4, 1955 FOREIGN PATENTS 730,781 Great Britain June 1, 1955 

